The present invention relates generally to blade dampers for damping vibratory responses of blades in turbine engines such as gas turbine aircraft engines.
Turbine engines have a stator and one or more rotors. Each rotor has rows of blades mounted on one or more disks rotatably mounted on the stator. The blades and disks have natural frequencies at which they resonate when excited. As the blades and disks resonate, stresses in the blades and disks rise and fall. Over time these oscillating stresses can cause the blades and/or the disks to fail due to material fatigue. The magnitudes of the oscillating stresses in the blades and disks can be reduced and the part lives can be increased by damping the vibratory response of these parts.
Various types of blade dampers have been developed to dampen vibratory responses. For example, some blades include shrouds extending between airfoils of adjacent blades to dampen vibratory response. Although connecting adjacent blades with shrouds can effectively dampen vibratory response, the shrouds increase blade weight and resulting stresses. Because stresses increase with rotational speed, shrouds may not be useable on blades which are intended to rotate at high speeds such as high pressure turbine blades of aircraft engines.
Another type of damper is an under-platform damper which is positioned between the disk and the blade. As the rotor rotates, these dampers are forced radially outward to simultaneously engage inboard facing surfaces of adjacent blades. The friction between the dampers and blades dampens the vibrations of the blades thereby reducing the vibratory stresses and increasing the blade life. Moreover as will be appreciated by those skilled in the art, the dampers are carried by the blades so the friction between blades and the disks increases and loading on portions of the blades and the disk increases. This increased friction and loading also affects the vibratory response of the blades. Some of these under-platform dampers have an additional advantage in that they seal gaps between adjacent blades to improve cooling air flows between the blades and disk.
Among the several features of the present invention may be noted the provision of a turbine engine blade damper for damping vibrations of blades in a turbine engine. The blade damper includes an elongate body extending between a forward end and a rearward end opposite the forward end. The body is sized and shaped for receipt within a gap formed between adjacent platforms of the blades so the body frictionally engages the adjacent platforms to dampen vibrations of the blades and to prevent air from passing through the corresponding gap during engine operation. The damper also includes a retainer mounted on at least one of the forward and rearward ends of the body. The retainer is sized and shaped for receipt within a recess formed in at least one of the adjacent blades to hold the body between the blades. The retainer is sized and shaped to prevent air from passing between the blades and the retainer during engine operation.
In another aspect, the present invention includes a method of manufacturing a turbine engine blade damper for damping vibrations of blades in a turbine engine. The method comprises the steps of cutting a wire to a length corresponding to a groove formed in a blade platform with which the damper is to be used, and attaching a retainer to an end of the wire.
In yet another aspect, the present invention includes a turbine engine comprising a disk having a generally circular periphery and a plurality of blades mounted about the periphery of the disk. Each of the blades includes an airfoil extending outward from a platform. The engine also includes a damper for damping vibrations of the plurality of blades. The damper including an elongate body and a retainer mounted on at least one end of the body. The retainer is sized and shaped for receipt within a recess formed in at least one of the adjacent blades to hold the damper between the blades. The retainer prevents air from passing between the blades and the retainer during engine operation.
Other features of the present invention will be in part apparent and in part pointed out hereinafter.